风浪扰动对太湖梅梁湾水体总磷变化的驱动模式研究

Preliminary study on the contribution model of wind wave disturbance to the variation of total phosphorus in Meiliang Bay of Taihu Lake

风浪扰动下的底泥再悬浮是浅水湖泊水体底泥内源性磷向水体释放的关键驱动因子。水体总磷(TP)受底泥内源磷释放过程影响频繁波动。基于风浪扰动强度与底泥悬浮物(SS)浓度定量关系模型,采用太湖原位未扰动柱状底泥开展水体底泥再悬浮过程模拟研究,分别模拟在小风(搅拌强度100~125 r/min)、大风(搅拌强度200~220 r/min)模式下底泥内源释放过程,探究风浪扰动对太湖梅梁湾水域TP浓度波动的贡献。结果表明,风浪扰动显著增加(P<0.01)了水体SS,小风与大风下水体SS均值分别增加了80.9%与360.8%,但随着扰动周期的延长,风浪扰动的效果会削弱。不同风浪扰动强度下水体TP均呈先上升后下降趋势。小风下水体TP为0.08~0.20 mg/L;大风下水体TP为0.09~0.34 mg/L。与对照组相比,小风组水体TP浓度呈现显著下降的趋势(P<0.05),而大风组水体TP浓度则表现为显著上升的趋势(P<0.01)。此外,大风持续扰动增加了水体TP浓度,但效果不显著(P>0.05)。风浪扰动致使0~3 cm底泥内的TP含量有所提高,底泥表面氧化还原条件的改变是底泥TP含量增加的主要原因。风浪扰动可能是表层底泥和间隙水TP升高的关键驱动因子。

Sediment resuspension under wind wave disturbance is the key element for internal phosphorus release from sediments in shallow lakes.Frequent fluctuation of total phosphorus(TP)in water body was caused by the release process of internal phosphorus.Based on the quantitative relationship model between wind wave disturbance intensity and sediment suspended solids(SS)concentration,this study used undisturbed in-situ columnar sediments of Taihu Lake to simulate the process of sediment resuspension,simulated the phosphorus release from sediments under light wind(100-125 r/min)and strong wind(200-220 r/min)modes respectively,and explored the contribution of wind wave disturbance to the fluctuation of TP concentration in Meiliang Bay water of Taihu Lake.The results showed that the wind wave disturbance significantly increased(P<0.01)the concentration of SS in water body.The average SS of the water body increased by 80.9%and 360.8%respectively in light wind and strong wind groups,but with the extension of the disturbance period,the effect of the wind wave disturbance would be weakened.The TP of water body showed a trend of first rising and then declining under different wind wave disturbance intensities.The range of TP under the condition of light wind was 0.08-0.20 mg/L,and under strong wind condition,the range was 0.09-0.34 mg/L.Compared with the control group,the TP concentration in water body of the light wind group showed a significant downward trend(P<0.05),while the TP concentration in water body of the strong wind group showed a significant upward trend(P<0.01).In addition,the continuous disturbance under strong wind condition increased the TP concentration of water body,but was not significant(P>0.05).The contents of TP in the surface sediments within 0-3 cm experienced an increase slightly due to wind wave disturbance.The main explanation was that the redox condition on the sediment surface changed.Overall,these results provided that the increase of wind wave disturbance intensity was the key element for the increase of TP in surface sediment and pore water.